st: RE: merging - unique observations

[Joe Canner <jcanner1@jhmi.edu>]

Andrew,

It is difficult to say for sure what the problem is without more details about your data, what command(s) you ran, and the exact error message you received.

However, it appears that at least one of the problems is that your first data set has multiple observations per country-pair (one for each year) while the second data set has only one observation per country-pair.  If this is the case, try a many-to-one merge:
. merge m:1 countrypair using distancedata
 
I can also imagine other problems that might arise from the use of country-pairs as the merging key, but we would have to know more about your data in order to diagnose them.

Regards,
Joe Canner
Johns Hopkins University School of Medicine

________________________________________
From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] on behalf of Andreas Dimopoulos [ad382@sussex.ac.uk]
Sent: Saturday, April 05, 2014 5:47 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: merging - unique observations

Good evening,

I have two datasets where the first one contains pairs of countries and
their in between trade for different years and another dataset which has
the pair of countries and their in between distance etc (which don't change
over time). I tried to merge those two datasets based on the things I have
read but stata tells me that the observations cannot be uniquely
identified.

Any piece of advise?

Regards,
Andrew
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